JP4423400B2 - Laminated structure strengthening method by two-layer brazing - Google Patents

Description

  The present invention relates to brazing technology for joining materials, and more particularly to brazing of a fine plate fin type compact heat exchanger used in the nuclear industry and general industrial fields.

  Conventionally, in a heat exchanger, when a high heat transfer surface density and a heat flux are required, a plate fin type heat exchanger has been used. In addition, when a particularly high heat exchange capability is required, such as a regenerative heat exchanger used in a helium gas cooled HTGR turbine system, a plate fin type heat exchanger using fine offset fins may be used. Conceivable. This fine plate fin type compact heat exchanger (FIG. 1) generally has a problem that it is difficult to ensure pressure resistance because the strength of the brazed portion is not so high in the conventional brazing technique. When the strength test of the fine plate fin is performed, it has been found that the destruction due to the internal pressure is observed particularly in the fine plate fin side portion (portion not joined to the separator) (FIG. 2).

  If the heat exchanger design specifications require further expansion of the heat transfer area and reduction of the heat exchanger dimensions, it is necessary to make the fins finer according to the requirements. There is a need to improve the strength of the fin side because it must be designed thin.

  Accordingly, an object of the present invention is to solve the problems of the prior art, such as ensuring the pressure resistance of the brazed portion and improving the strength of the fine plate fins in the fine plate fin type compact heat exchanger.

In order to solve the above-mentioned problems of the prior art, the present inventors have conducted intensive research and completed the present invention.
In short, the present invention is an offset fin used in a plate fin type heat exchanger, wherein a base material having a three-layer structure of brazing material / base material / brazing material is used as the offset fin plate, and the plate and separator are used. It is formed by inserting a brazing material sheet between them, melting it and brazing the plate and the separator, and covering the entire surface with a brazing layer.

Moreover, this invention makes the problem-solving means the offset fin type heat exchanger which has the high temperature pressure | voltage resistant structure using said offset fin.
Further, the present invention is a method of strengthening a laminated structure by two-layer brazing of offset fins used in a plate fin type heat exchanger, wherein a three-layer structure of Ni brazing material / base material / Ni brazing material is used as an offset fin plate. A base material is used, brazing is performed by interposing a Ni brazing material sheet between the plate and the separator, and the base material is strengthened by forming a high strength brazing reaction layer. .

  By using the heat exchanger having the three-layer structure fin of the present invention, the high-temperature gas furnace gas turbine system can be made more compact and high-performance, and an economic merit is born in the plant. Further, according to the present invention, gas / gas heat exchange can be performed under the conditions shown in Table 2.

  The present invention relates to an offset fin used in a plate fin type heat exchanger, wherein a base material having a three-layer structure of brazing material / base material / brazing material is used as an offset fin plate, and between the plate and the separator. It is formed by inserting a brazing material sheet, melting it and brazing the plate and the separator, and covering the entire surface with a brazing layer.

  In the present invention, the material of the offset fin plate and the plate may be any material as long as it is allowed in consideration of operating temperature, pressure, etc., for example, a SUS material can be used, and its dimensions are in accordance with the specifications. Just design. Ni brazing filler metal can be used as the brazing filler metal.

  In FIG. 3, the conceptual diagram which shows the offset fin three-layer structure part by the two-layer brazing method of this invention is shown. In the conventional brazing method shown in (a), the strength of the portion where the fin plate and the separator are not joined (fin side portion) is weak as shown in FIG. However, a three-layer structure having improved high-temperature strength and fatigue strength could be realized by the two-layer brazing method in which both surfaces of the fin plate of the present invention shown in FIG.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to an Example.

In this example, a three-layer reinforced offset fin element strength test piece was manufactured, and a high temperature strength / fatigue test was performed on the test piece. First, a manufacturing procedure is shown below.
(A) Manufacture of three-layer structure fin and parts processing In order to make an offset plate fin type heat exchanger having a structure as shown in FIG. 1, each part having the dimensions shown in Table 1 was manufactured using SUS304.

What is particularly important here is the three-layer structure of the offset fin (core). In order to manufacture a three-layer offset fin, Ni brazing thin film (amorphous tape brazing MBF20 (made by Hoshiden Co., Ltd.), thickness 38 μm) is laid on the upper and lower surfaces of a 0.15 mm thin plate used as an offset fin substrate. the by a double punching method shown in FIG. 5, fold the fin uneven shape. Specifically, in FIG. 5 , the plywood is first fixed by the upper fixed die and the lower fixed die (a → b), and then the plywood is pushed up by the lower movable die and deformed along the notch portion of the upper fixed die. (B → c) Next, the plywood is pushed down by the upper movable die and deformed along the cutout portion of the lower movable die (c → d), and thereafter, the same procedure is repeated to form the uneven shape. . This method is effective for processing a three-layer plywood because the fin processing accuracy is higher and the brazing thin film is less damaged than the method of folding a fin in a single operation using an uneven mold.

(B) Assembling multi-stage fins Using a rectangular assembly jig, a brazing material is attached to the plate and welded and fixed in the order of a closing plate (separator). It was. Subsequently, the multi-stage fins were assembled in the same manner, and the multi-stage fins were assembled while being restrained by a jig.

(C) Vacuum brazing Placed in a vacuum furnace with multistage fins constrained temporarily assembled, vacuum brazing is performed under the processing conditions of vacuum degree 1 × 10 ⁵ torr, maximum temperature 1,323 ~ 1,373K, maximum holding time 10 ~ 15 minutes. went.

  The results of the high temperature strength / fatigue test are shown in FIG. In the figure, the closed (black) symbol is the two-layer brazing material according to the present invention, the open (white) symbol is the conventional material, the ○ □ is the strength and 0.2% guarantee, respectively, and the broken line is the SUS304 mother for comparison It is a material. As shown in the figure, the high temperature strength was about 1.8 times that of the SUS304 base material.

  In accordance with the present invention, both sides of the fin side wall portion made of SUS304 base metal were brazed with Ni brazing material to form a Ni-based high-strength brazing reaction layer on both sides, thereby strengthening the base material.

FIG. 1 is a conceptual diagram of an offset plate fin heat exchanger. (A) is a top view, (b) is a side view. FIG. 2 shows a state of a strength test of a fine plate fin side portion having a laminated structure, and (a) shows a state before the test and (b) a state after the test. FIGS. 3A and 3B are conceptual diagrams showing a three-layer structure of an offset fin according to the two-layer brazing method of the present invention. FIG. 3A shows a conventional brazing method and FIG. 3B shows a brazing method according to the present invention. FIG. 4 is a diagram showing a high-temperature strength / fatigue test of a fin specimen by two-layer brazing. FIG. 5 is a conceptual diagram of a fine fin processing procedure (double action method) from a three-layer thin plate (brazing material / fin material / brazing material).

Claims (2)

A method for manufacturing a three-layer structure offset fin of a brazing material / base material / brazing material used for a compact plate fin type compact heat exchanger, which is made of an amorphous tape-shaped Ni brazing on both upper and lower surfaces of a 0.15 mm thick offset substrate A method comprising processing a plywood obtained by spreading a thin film into a concavo-convex shape and then vacuum brazing . A 0.1 μm thick offset substrate with 38 μm thick Ni brazing thin film on both upper and lower surfaces,
The obtained plywood is fixed to the upper fixed die and the lower fixed die, the plywood is pushed up by the lower movable die and deformed along the notch of the upper fixed die, and then the plywood is pushed down by the upper movable die. Repeatedly deform along the notch portion of the fixed die to form an uneven shape,
A method for producing a three-layer structure offset fin of brazing material / base material / brazing material for use in a compact plate fin type compact heat exchanger according to claim 1 .

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